Which word in bold means “to exchange with another type”?

What type of figurative language is used in this passage from "letter from birmingham jail"? just as the prophets of the eighth century b. c. left their villages and carried their "thus saith the lord" far beyond the boundaries of their hometowns, and just as the apostle paul left his village of tarsus and carried the gospel of jesus christ to the far corners of the greco roman world, so am i compelled to carry the gospel of freedom beyond my own hometown. allusion symbolism imagery metaphor

In concrete mixers what seems to be the speakers feeling about the concrete mixers

Hich statement offers the best comparison of the two poems? where have you gone." i am a black woman.